How does image resolution play out on my computer monitor?

The computer screen you are looking at right now is set at a particular resolution. The larger the screen, the larger you likely have your screen resolution set. If you have a 19” monitor, likely you have it set at 1440 × 900 pixels. If you have a 24” screen it is likely set at 1920 × 1200. You can change the settings but these are optimum for those screen sizes. Now, if your monitor is set to 1920 × 1200 and you open an image that is 1440 × 900, it will only fill up a part of your screen. If you open an image that is 2048 × 1536 (3.1 megapixels) then you will find yourself moving the slider bar around to see all the different parts of the image. It just won’t fit. Add to that the fact that the computer monitor has a finite number of pixels per inch available (like 72) so if you are going to display your image on a monitor only, you would want to drop the quality down to 72 to save file space. If you are going to put your image on a webpage or email it to a friend, then you will want to first make it a useful size. Not too big, not too small. Maybe 200-300 pixels high would be a nice size. You can also reduce the size of the file (not necessarily the size of the image) so it loads faster.